Drinking water can become contaminated with enteric viruses and pose a significant health risk to people. These viruses enter source waterways through the direct or indirect discharge of treated and untreated human and animal waste into rivers, streams and estuaries. In general, waterborne human enteric viruses pose a greater health risk than enteric bacteria due to the low infectious dose, which may be as little as one virion [Girones, R, et al., Wat. Sci. Technol. (1993) 27, 235-241].
Waterborne enteric viruses replicate in the gastrointestinal tract and are shed in the feces of infected individuals. Most enteric viruses are morphologically similar, and consist of an icosahedral-shaped, non-enveloped capsid, which surrounds a single-stranded RNA (e.g. Norwalk-like virus) or double stranded DNA (e.g. adenovirus) molecule. Noroviruses and Hepatitis A are the most common enteric viruses transmitted by water [Koopmans M, and Duizer E., Int J Food Microbiol. (2004) 90(1):23-41]. Other common waterborne viruses include rotaviruses, echoviruses, coxsackieviruses and adenoviruses. Several of these viruses can be found on the Drinking Water Contaminant Candidate List as issued by the Environmental Protection Agency.